The invention arose during continuing development efforts relating to the subject matter of U.S. Pat. Nos. 4,665,549, 4,677,676, 4,677,677, 4,736,431, 4,815,139, 4,837,834, incorporated herein by reference.
The present invention involves an intercom communication system with active acoustic attenuation. One particularly desirable application of the invention is in magnetic resonance medical imaging systems where the patient is in a noisy environment in the hollow interior tunnel of a cylindrical tubular structure subject to magnetic hum and the like. The patient has difficulty hearing the attending medical technician, and vice versa, and it is thus difficult to communicate instructions, symptoms, etc. Furthermore, the noise adds to the discomfort of the patient who may already be apprehensive of the medical procedure and the claustrophobic tunnel. The present invention cancels the noise and quiets the environment within the tunnel, and also enables communication from the patient to the medical technician, and vice versa.
Another application of the invention is the quieting of the interior of a motor vehicle where the driver or passengers are exposed to noise introduced by the engine, exhaust system, tires, etc. In this environment, the noise is annoying and prevents enjoyment of the vehicle entertainment system and hinders communication with the vehicle via radio telephone. The present invention cancels the noise and and quiets the environment, and also enables enjoyment of the entertainment system and communication to the vehicle via radio telephone, and vice versa.
The invention has numerous other applications where communication is desired in noisy environments.